//===-- llvm/BasicBlock.h - Represent a basic block in the VM ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the BasicBlock class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_BASICBLOCK_H
#define LLVM_BASICBLOCK_H
#include "llvm/Instruction.h"
#include "llvm/SymbolTableListTraits.h"
#include "llvm/ADT/ilist.h"
#include "llvm/Support/DataTypes.h"
namespace llvm {
class TerminatorInst;
template<> struct ilist_traits
: public SymbolTableListTraits {
// createSentinel is used to get hold of a node that marks the end of
// the list...
// The sentinel is relative to this instance, so we use a non-static
// method.
Instruction *createSentinel() const {
// since i(p)lists always publicly derive from the corresponding
// traits, placing a data member in this class will augment i(p)list.
// But since the NodeTy is expected to publicly derive from
// ilist_node, there is a legal viable downcast from it
// to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
// NodeTy, which becomes the sentinel. Dereferencing the sentinel is
// forbidden (save the ilist_node) so no one will ever notice
// the superposition.
return static_cast(&Sentinel);
}
static void destroySentinel(Instruction*) {}
Instruction *provideInitialHead() const { return createSentinel(); }
Instruction *ensureHead(Instruction*) const { return createSentinel(); }
static void noteHead(Instruction*, Instruction*) {}
private:
mutable ilist_node Sentinel;
};
/// This represents a single basic block in LLVM. A basic block is simply a
/// container of instructions that execute sequentially. Basic blocks are Values
/// because they are referenced by instructions such as branches and switch
/// tables. The type of a BasicBlock is "Type::LabelTy" because the basic block
/// represents a label to which a branch can jump.
///
/// A well formed basic block is formed of a list of non-terminating
/// instructions followed by a single TerminatorInst instruction.
/// TerminatorInst's may not occur in the middle of basic blocks, and must
/// terminate the blocks. The BasicBlock class allows malformed basic blocks to
/// occur because it may be useful in the intermediate stage of constructing or
/// modifying a program. However, the verifier will ensure that basic blocks
/// are "well formed".
/// @brief LLVM Basic Block Representation
class BasicBlock : public Value, // Basic blocks are data objects also
public ilist_node {
public:
typedef iplist InstListType;
private:
InstListType InstList;
Function *Parent;
void setParent(Function *parent);
friend class SymbolTableListTraits;
BasicBlock(const BasicBlock &); // Do not implement
void operator=(const BasicBlock &); // Do not implement
/// BasicBlock ctor - If the function parameter is specified, the basic block
/// is automatically inserted at either the end of the function (if
/// InsertBefore is null), or before the specified basic block.
///
explicit BasicBlock(const std::string &Name = "", Function *Parent = 0,
BasicBlock *InsertBefore = 0);
public:
/// Instruction iterators...
typedef InstListType::iterator iterator;
typedef InstListType::const_iterator const_iterator;
/// Create - Creates a new BasicBlock. If the Parent parameter is specified,
/// the basic block is automatically inserted at either the end of the
/// function (if InsertBefore is 0), or before the specified basic block.
static BasicBlock *Create(const std::string &Name = "", Function *Parent = 0,
BasicBlock *InsertBefore = 0) {
return new BasicBlock(Name, Parent, InsertBefore);
}
~BasicBlock();
/// getParent - Return the enclosing method, or null if none
///
const Function *getParent() const { return Parent; }
Function *getParent() { return Parent; }
/// use_back - Specialize the methods defined in Value, as we know that an
/// BasicBlock can only be used by Instructions (specifically PHI nodes and
/// terminators).
Instruction *use_back() { return cast(*use_begin());}
const Instruction *use_back() const { return cast(*use_begin());}
/// getTerminator() - If this is a well formed basic block, then this returns
/// a pointer to the terminator instruction. If it is not, then you get a
/// null pointer back.
///
TerminatorInst *getTerminator();
const TerminatorInst *getTerminator() const;
/// Returns a pointer to the first instructon in this block that is not a
/// PHINode instruction. When adding instruction to the beginning of the
/// basic block, they should be added before the returned value, not before
/// the first instruction, which might be PHI.
/// Returns 0 is there's no non-PHI instruction.
Instruction* getFirstNonPHI();
const Instruction* getFirstNonPHI() const {
return const_cast(this)->getFirstNonPHI();
}
/// removeFromParent - This method unlinks 'this' from the containing
/// function, but does not delete it.
///
void removeFromParent();
/// eraseFromParent - This method unlinks 'this' from the containing function
/// and deletes it.
///
void eraseFromParent();
/// moveBefore - Unlink this basic block from its current function and
/// insert it into the function that MovePos lives in, right before MovePos.
void moveBefore(BasicBlock *MovePos);
/// moveAfter - Unlink this basic block from its current function and
/// insert it into the function that MovePos lives in, right after MovePos.
void moveAfter(BasicBlock *MovePos);
/// getSinglePredecessor - If this basic block has a single predecessor block,
/// return the block, otherwise return a null pointer.
BasicBlock *getSinglePredecessor();
const BasicBlock *getSinglePredecessor() const {
return const_cast(this)->getSinglePredecessor();
}
/// getUniquePredecessor - If this basic block has a unique predecessor block,
/// return the block, otherwise return a null pointer.
/// Note that unique predecessor doesn't mean single edge, there can be
/// multiple edges from the unique predecessor to this block (for example
/// a switch statement with multiple cases having the same destination).
BasicBlock *getUniquePredecessor();
const BasicBlock *getUniquePredecessor() const {
return const_cast(this)->getUniquePredecessor();
}
//===--------------------------------------------------------------------===//
/// Instruction iterator methods
///
inline iterator begin() { return InstList.begin(); }
inline const_iterator begin() const { return InstList.begin(); }
inline iterator end () { return InstList.end(); }
inline const_iterator end () const { return InstList.end(); }
inline size_t size() const { return InstList.size(); }
inline bool empty() const { return InstList.empty(); }
inline const Instruction &front() const { return InstList.front(); }
inline Instruction &front() { return InstList.front(); }
inline const Instruction &back() const { return InstList.back(); }
inline Instruction &back() { return InstList.back(); }
/// getInstList() - Return the underlying instruction list container. You
/// need to access it directly if you want to modify it currently.
///
const InstListType &getInstList() const { return InstList; }
InstListType &getInstList() { return InstList; }
/// getSublistAccess() - returns pointer to member of instruction list
static iplist BasicBlock::*getSublistAccess(Instruction*) {
return &BasicBlock::InstList;
}
/// getValueSymbolTable() - returns pointer to symbol table (if any)
ValueSymbolTable *getValueSymbolTable();
/// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const BasicBlock *) { return true; }
static inline bool classof(const Value *V) {
return V->getValueID() == Value::BasicBlockVal;
}
/// dropAllReferences() - This function causes all the subinstructions to "let
/// go" of all references that they are maintaining. This allows one to
/// 'delete' a whole class at a time, even though there may be circular
/// references... first all references are dropped, and all use counts go to
/// zero. Then everything is delete'd for real. Note that no operations are
/// valid on an object that has "dropped all references", except operator
/// delete.
///
void dropAllReferences();
/// removePredecessor - This method is used to notify a BasicBlock that the
/// specified Predecessor of the block is no longer able to reach it. This is
/// actually not used to update the Predecessor list, but is actually used to
/// update the PHI nodes that reside in the block. Note that this should be
/// called while the predecessor still refers to this block.
///
void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs = false);
/// splitBasicBlock - This splits a basic block into two at the specified
/// instruction. Note that all instructions BEFORE the specified iterator
/// stay as part of the original basic block, an unconditional branch is added
/// to the original BB, and the rest of the instructions in the BB are moved
/// to the new BB, including the old terminator. The newly formed BasicBlock
/// is returned. This function invalidates the specified iterator.
///
/// Note that this only works on well formed basic blocks (must have a
/// terminator), and 'I' must not be the end of instruction list (which would
/// cause a degenerate basic block to be formed, having a terminator inside of
/// the basic block).
///
BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = "");
};
} // End llvm namespace
#endif